基于“热”激子过程的高效率深蓝光材料的设计及其激发态调节

In the fields of the fluorescence materials preparation and their relevant theoretical study, it is becoming a critical problem to realize the high color-saturation, high quantum yield and high exciton utilization efficiency in non-doped deep-blue emission devices. In this project, the phenanthroimidazole (PIM) was chosen as a basic building block basing on the hot-exciton theory, and their derivatives were processing in two dimensional direction with class D-A structures. By changing the substituted groups at C2, N1 and the phenanthrene substituted positions, the values and proportions of local excited state (LE) and charge-transfer (CT) state in hybridized excited state of PIM derivatives were adjusted. Under the control of blue color purity, the delocalized electrons in effective conjugation system were maximally utilized from the electronic cloud overlap characteristics between phenanthrene substituted plane and C2 substituted group, which was benefit to improving the quantum efficiency. Because the N1-group had a relatively independent electronic cloud structure, we can flexibly adjust the energy levels of CT states, and tuning the RISC process. At the same time, the suitable two-dimensional cross dipole structure could increase the value of ΔET1T2, and promoted the exciton transformation from T form to S one. Basing on the synthesis of PIM derivatives in this project, combining with their theory simulation results originating from basically photophysical and photochemical principles, and the performance analysis of non-doped devices, we would develop a kind of high efficiency (high quantum efficiency and high exciton utilization) deep-blue light materials and the relative molecular design theory.

如何使非掺杂型深蓝光材料兼顾高的量子效率和高的激子利用率，一直是发光材料及器件制备和理论研究领域中亟待解决的问题。本项目拟从热激子理论出发，以菲并咪唑(PIM)为基本构筑基元，提出在“二维”方向上同时构筑D-A结构的设想，通过系统地改变菲基、C2及N1取代基团的结构和位置，来调节PIM衍生物杂化激发态中局域态(LE)和电荷转移态(CT)分布。在保证蓝光色纯度的前提下，利用菲基平面与C2取代基元大的电子云重叠特性，最大限度地利用有效共轭体系内离域电子，达到提高量子效率的目的；借助N1取代基相对独立的电子云结构，灵活地调节CT态能级，增加激子的反隙间穿越效率。同时，适宜强度二维交叉偶极结构能增加ΔET1T2，促进T激子向S激子的转化。本项目以有机合成为基础，结合基态-激发态理论计算、溶液-固态光谱和非掺杂型器件性能等数据分析，发展一类高效率（高量子效率和高激子利用率）深蓝光材料及分子设计理论。

如何使非掺杂型深蓝光材料兼顾高的量子效率和高的激子利用率，一直是发光材料及器件制备和理论研究领域中亟待解决的问题。本项目从热激子理论出发，以菲并咪唑（PIM）为核心构筑基元，通过系统地改变C2、N1和菲基上取代基团的结构和位置，确认了其具有显著“二维”方向修饰特性，并可以实现对PIM衍生物杂化激发态中局域态（LE）和电荷转移态（CT）的组成和分布的调控；在保证发光色纯度和效率的前提下，实现三线态激子向单线态激子的有效转化，将激子利用率提高至近100%。通过拓展轴共轭形式实现了PIM的长短轴的互换，结合链接位点电子杂化形式和空间位阻因素，发现吡咯型N元素和空阻型C元素具有构筑分离长轴LE和短轴CT的节点优势。因此，逐步提出“交叉长短轴”策略在构筑电致饱和深蓝光材料中的重要意义。同时，我们还尝试了该策略在不同基元结构（吖啶酮、咔唑、噻咯、萘并噻二唑体系）中的应用，获得了一系列性能优异的电致发光材料，也为后续理论的完善奠定了基础。另外，我们将调整LE/CT分布对于激子转化途径影响应用在光致发光领域，开发一系列具有高聚集态发光性能的荧光探针和智能材料，并拓展其在传感、生物和医学等领域的应用。